侧积交错层──辫状河道的主要沉积构造类型

LATERAL ACCRETION CROSS-BEDDING：THE MAIN TYPE OF SEDIMENTARYSTRUCTURES IN THE BRAIDED CHANNEL

李维锋 高振中 彭德堂

Li Weifeng Gao Zhenzhong Peng Detang

江汉石油学院地质系, 湖北荆沙434102

Jianghan Petroleum Institute, Hubei 434102

侧积交错层是砂体侧向迁移加积所形成。在辫状河道砂体中特别发育,其特点:①层系的整体形态呈板状,而细层呈“S”形弯曲,向上,向下收敛明显;②侧积交错层的某些细层内部可见次一级的前积交错层及沿塌构造;③层系厚度与沉积物粒度无关;④同一层系内各细层的厚度、成分和粒度有较大差异;⑤细层倾向垂直干区域古流向。辫状河道中侧积交错层发育原因是:横向环流的普遍存在;沉积物中富砂少泥。

Lateral accretion cross-bedding results from lateral accretion of sand bodies induced bythe lateral migration of channels and is very abundant in the braided channels. Its characteristics are: ① the overall shape of its sets is tabular, but its laminae are sigmoid, clearlyconverging both upward and downward. ② there is secondary cross-bedding or crosslaminations as well as slump structures in the inner part of some‘laminae'. ③ the setthickness has nothing to do with the grain size of the sediments. ④ the thickness, grainsize and composition of each lamination within the same set are significantly different eachother. ⑤the laminae dip is at approximate vertical angles to palaeocurrent direction. Thelateral accretion cross-beddings are very abundant in the braided channel as there are moretransverse circulation flows in it and more sand and less mud in the sediments.

“八五”国家重点科技攻关项目

https://doi.org/10.11781/sysydz199603298